Anticonvulsive effect of urethane on aminopyridine-induced epileptiform activity

The effects of urethane anaesthesia on the development and spread of ictal-like epileptiform activity induced by 3-aminopyridine, was investigated on the somatosensory cortex of rats. Under urethane anaesthesia in most animals only one abortive ictal period appeared with dose-dependent latency. Urethane completely abolished high frequency afterdischarges (5-10 Hz) and prevented the development of recurrent seizures in both primary and mirror foci. Urethane also eliminated ongoing epileptiform activity induced previously by 3-aminopyridine under nembutal anaesthesia. The antiepileptic effects of urethane on ictal-like activity may be the consequence of a presynaptic action through reduction of glutamate-mediated excitation together with a depressant effect on responsiveness of cortical neurones. The afterdischarges of high frequency could be essential to development and stabilization of repetitive tonic events in the neocortex.